London: Cyclist Sarah Storey stormed to her eighth Paralympic gold, taking the women's C5 individual 3km pursuit after a lightning-quick qualifying time that would have won her a non-disabled title.

The 34-year-old rider's winning performance, which opened the hosts' gold account, came amid a slew of new world bests in track cycling and swimming, as China took the first gold of the Games on the first day of competition.

Storey, a five-time Paralympic swimming gold medallist who switched sports for the Beijing Games in 2008, caught Poland's Anna Harkowska with just under half of the 12-lap race to go, giving her a third cycling gold.

The British cyclist earlier clocked a new world best of 3min 32.170sec, which would have won her silver at the World Championships earlier this year and the title at the UCI Track Cycling World Cup at the same venue in February. That World Cup race, a test event for the Olympic Velodrome, was won by her British compatriot Joanna Rowsell in 3min 32.364sec. She took Olympic gold earlier this month in the team pursuit.

Storey, who was born without a functioning left hand and narrowly missed out on a place in Britain's Olympic squad, said: "I always thought that if I could get off to a great start it would set up the week and hopefully that's the case.

"To get the gold medal is a dream come true." China won both races in the C1-2-3 pursuit, with Zeng Sini breaking the world record in qualifying, while Germany's Tobias Graf set a new C2 best as he won bronze in men's event.

Susan Powell posted the world's fastest time in the women's C4 3km individual pursuit qualifiers and went on to give Australia its first gold of the Games.

It was a good day for the Aussies, with defending champion Kieran Modra and guide rider Scott McPhee taking the men's blind and visually impaired 4km tandem pursuit, beating Modra's previous world best.

Five world records tumbled in the swimming finals, with the highlight New Zealander Sophie Pascoe, who smashed the new best she set earlier in qualifying by more than three seconds in the final of the 200m SM10 individual medley.

In the men's equivalent, Benoit Huot of Canada shaved his own previous world best down to 2min 10.01secs.

Zheng Tao, meanwhile, finally beat the record set by Russia's Igor Plotnikov way back in 2004 in the men's S6 100m backstroke, while compatriot Lu Dong took the women's race, also in world record time, as China scooped three golds.

Brazil's Daniel Dias became the fastest man ever in the S5 50m freestyle. Sergey Punko and Oxana Savchenko made it a Russian double in both S12 400m freestyle events.

Charles Rozoy gave France its first gold in the men's S8 100m butterfly and US swimmer Jessica Long took the women's race to give her an eighth Paralympic gold over three Games.

Britain's Jonathan Fox, who lowered his own S7 100m backstroke world record to 1min 9.86secs in qualifying, went on to secure the hosts' first gold in the pool, while Hungarian powerhouse Tamas Sors took the S9 100m butterfly.

In the women's race, South Africa's Natalie du Toit won the 11th gold in her Paralympic career -- even if she was disappointed with the time.

Du Toit, a dominant force over the last decade who became the first amputee to qualify for the Olympics, swimming the 10km open water race in Beijing, plans to race in seven events and is retiring after the Games.

But she ruled out staying on in the sport until the next Games in Rio de Janeiro in four years' time.

"No I'm done. It's very official. It's sad, but I walk away knowing I gave it everything," she said.

China's Zhang Cuiping earlier shot her way to the first gold of the Games in the women's 10m air rifle, scoring 104.9 for an overall score of 500.9, while Park Seakyun, of South Korea, won the men's 10m air pistol.

Nigeria secured their first win in powerlifting, as Yukubu Adesokan was roared to gold in the men's -48kg class, as he broke his own world record twice to lift nearly four times his own body weight, first with 178kg then 180kg.

And there was double delight for German twins Carmen and Ramona Brussig, who both won judo gold in the women's -48kg and -52kg categories.